Geology topics
Find USGS publications on mineral resources and deposits. Search commodities and geographic names, then check source reports for geology and assessment methods.
An interagency report prepared by the U.S. Geological Survey Saudi Arabian Mission for the Ministry of Petroleum and Mineral Resources, Kingdom of Saudi Arabia. The work on which this report was based was performed in accordance with a cooperative agreement between the U.S. Geological Survey and the Ministry of Petroleum and Mineral Resources.
In this report, subjects discussed include components of mineral supply, production, and consumption data, and information on selected mineral commodities in which the Energy Critical Elements Study Group has an interest, and U.S. Geological Survey (USGS) recycling studies, with some results of these studies.
A reexamination of reported blueschist mineral localities in the basal strata of the Great Valley sequence revealed only prehnite-pumpellyite facies minerals. Franciscan graywacke thrust below the Great Valley rocks contains lawsonite-quartz blueschist assemblages. At a common pressure of about 4 kb, the Franciscan blueschists formed at lower temperatures than the overlying Great Valley prehnite-bearing rocks, lending support to tectonic models that involve rapid subduction of the Franciscan rocks.
Bloedite, epsomite, and related minerals occur in small amounts throughout the arid eastern foothills of the Diablo and Temblor Ranges, as efflorescences on siliceous shale and as deposits around small springs and a brine pond. These minerals ultimately are products of weathering of underlying organic shale, and they are reminders that the chemistry of weathering of reduced organic shale is largely a reversal of the chemistry of its early diagenesis.
Stream water and sediment toxicity to aquatic insects were quantified from central Colorado catchments to distinguish the effect of geologic processes which result in high background metals concentrations from historical mining. Our sampling design targeted small catchments underlain by rocks of a single lithology, which allowed the development of biological and geochemical baselines without the complication of multiple rock types exposed in the catchment. By accounting for geologic sources of metals to the environment, we were able to distinguish between the environmental effects caused by mining and the weathering of different mineralized areas. Elevated metal concentrations in water and sediment were not restricted to mined catchments. Impairment of aquatic communities also occurred in unmined catchments influenced by hydrothermal alteration. Hydrothermal alteration style, deposit type, and mining were important determinants of water and sediment quality and aquatic community structure. Weathering of unmined porphyry Cu-Mo occurrences resulted in water (median toxic unit (TU) = 108) and sediment quality (TU = 1.9) that exceeded concentrations thought to be safe for aquatic ecosystems (TU = 1). Metalsensitive aquatic insects were virtually absent from streams draining catchments with porphyry Cu-Mo occurrences (1.1 individuals/0.1 m2 ). However, water and sediment quality (TU = 0.1, 0.5 water and sediment, respectively) and presence of metalsensitive aquatic insects (204 individuals/0.1 m2 ) for unmined polymetallic vein occurrences were indistinguishable from that for unmined and unaltered streams (TU = 0.1, 0.5 water and sediment, respectively; 201 individuals/0.1 m2 ). In catchments with mined quartz-sericite-pyrite altered polymetallic vein deposits, water (TU = 8.4) and sediment quality (TU = 3.1) were degraded and more toxic to aquatic insects (36 individuals/0.1 m2 ) than water (TU = 0.4) and sediment quality (TU = 1.7) from mined propylitically altered polymetallic vein deposits. The sampling approach taken in this study distinguishes the effects of different mineral deposits on ecosystems and can be used to more accurately quantify the effect of mining on the environment.
As a mineral resource, “phosphate rock” is defined as unprocessed ore and processed concentrates that contain some form of apatite, a group of calcium phosphate minerals that is the primary source for phosphorus in phosphate fertilizers, which are vital to agriculture.
Estimating numbers of undiscovered mineral deposits is a fundamental part of assessing mineral resources. Some statistical tools can act as guides to low variance, unbiased estimates of the number of deposits. The primary guide is that the estimates must be consistent with the grade and tonnage models. Another statistical guide is the deposit density (i.e., the number of deposits per unit area of permissive rock in well-explored control areas). Preliminary estimates and confidence limits of the number of undiscovered deposits in a tract of given area may be calculated using linear regression and refined using frequency distributions with appropriate parameters. A Poisson distribution leads to estimates having lower relative variances than the regression estimates and implies a random distribution of deposits. Coefficients of variation are used to compare uncertainties of negative binomial, Poisson, or MARK3 empirical distributions that have the same expected number of deposits as the deposit density. Statistical guides presented here allow simple yet robust estimation of the number of undiscovered deposits in permissive terranes.
Although chromium is a metal, it does not occur naturally in metallic form. Chromium can be found in many minerals, but the only economically significant chromium-bearing mineral is chromite. Chromite has been mined from four different deposit types: stratiform chromite, podiform chromite, placer chromite, and laterite deposits. Most of the world's resources, however, are located in stratiform chromite deposits, such as the Bushveld Complex in South Africa. The economic potential of chromite resources depends on the thickness and continuity of the deposit and on the grade of the ore. Many of the major stratiform chromite deposits also contain economic levels of platinum, paladium, rhodium, osmium, iridium, and ruthenium.
Iron phosphate minerals which cement talus ore below cliffs formed by massive magnetite- hematite deposits at Bomi hill, Liberia, and also occur in place in fissures and caves in the ore both at Bomi hill and Bambuta, were formed by the interaction of bat dung and iron oxides. The minerals include leucophosphite (previously known only from Western Australia), phosphosiderite, and strengite. Analyses of the leucophosphite are included.
The author has identified the following significant results. The discovery of copper mineralization along a lineament mapped in Area 7 (La Paz) has lent credence to the use of LANDSAT 1 data as a basic step in mineral exploration. In Area 9 (Copiapo Region), a number of lineaments were found to be associated with the largest copper deposits of the region. In Area 12 (Magallanes), the identification of what is believed to be a tertiary basin from LANDSAT 1 data has resulted in a new area for petroleum exploration. Band 7 images, as black and white transparencies, were found to be the most useful for geologic interpretation in both tropical vegetated areas and desert regions. Color composites made by the diazochrome process, chromaline process, and from color additive viewers provided additional information. Mosaics of LANDSAT 1 data covering 4 x 6 degrees of latitude and longitude compiled at the 1:1,000,000 scale were found to be an ideal size and format for most users.
Uranium deposits in the San Rafael Swell are related to sedimentary depositional environments in the Upper Triassic Chinle Formation. The sedimentary textures resulting from depositional processes operating in low-energy environments appear to have influenced uranium mineralization. The Ohinle consists of three fining-upward, fluvial-lacustrine sequences. Uranium minerals are concentrated in the lower part of the lowest sequence in areas where sediments of low-energy environments are complexly interbedded with sediments of other environments. Areas favorable for uranium exploration exist in the subsurface to the north, west, and south of the Chinle outcrop in the Swell. This determination is based on the spatial distribution of depositional environments and the pattern of Chinle deposition through time.
A soil chronosequence developed on marine terraces along coastal California, exhibits deeper and more intensively weathered mineral profiles with increasing age (65 to 226 kyrs). Feldspar concentrations generally increase linearly with terrace depth. The slope or weathering gradient is defined by the ratio of the weathering rate and the velocity at which the profile penetrates into the regolith.A spread sheet calculator further refines profile geometries, demonstrating that the non-linear regions at low residual feldspar concentrations are dominated by exponential changes in mineral surface to volume and at high residual feldspar concentrations by the approach to thermodynamic saturation.These parameters, in addition to the kinetic rate constant, are of secondary importance to the fluid flux qh which controls the weathering velocity and solute fluxes from the profile. © 2007 Taylor & Francis Group, London.
Weathering in the field tends to be incongruent due to the precipitation of secondary phases. However, most laboratory experiments are designed to avoid such precipitation, as it complicates the interpretation of the experimental results. Here we report on a new method that eliminates the effect of secondary phase precipitation on the determination of the dissolution rate of a primary mineral. The dissolution rate determination in the newmethod is based on measured changes in Si isotopic composition of a spiked solution.The newmethod significantly improves the accuracy in calculating near-equilibrium dissolution rates. Moreover, combining this method with measured Al concentration enables the determination of precipitation rate of secondary minerals. © 2007 Taylor & Francis Group, London.
The Pogo Au deposit is the largest of a number of gold occurrences in eastern interior Alaska, that occur along a broad trend from west of Pogo to Black Mountain. Some of these occurrences are hosted in amphibolite facies gneisses and others in mid-Cretaceous igneous rocks that intruded the older metamorphic rocks. All occurrences contain arsenopyrite and pyrite. Whole rock geochemical trends distinguish most metamorphic rock-hosted vein prospects (strong Bi-Te-Au correlations) and intrusion-hosted occurrences (weak As-Au correlations). Brecciated quartz veins in metamorphic rocks have paragentically late Bi-Te (±S) + Au that post-dates Fe-As sulphide deposition. High grade vein samples from the Tibbs Creek intrusion-hosted deposits contain pyrite and arsenopyrite, generally lack Bi-Te minerals, but can contain paragentically younger euhedral quartz, stibnite and carbonate. Cathodoluminescence studies of gold-rich samples indicate that quartz dissolution occurred during the syn- to post-tectonic Bi-Te-Au deposition, and the later stibnite event. In the case of metamorphic rock-hosted deposits (e.g., Pogo, Gray Lead), Bi-Te and gold deposition commonly occurs in microfractures within quartz veins; the limited quartz in these fractures have distinctive CL response. We propose that gold deposition is related to changes in P-T conditions rather than fluid-rock chemical reactions. Similar quartz dissolution textures affect the void-filling euhedral quartz before or during stibnite and carbonate mineralization in the high-grade Au samples from Blue Lead.
This review summarizes significant exploration trends related to active sites and budgets, mineral commodities and regional factors for the years 2001-2015. Data were compiled by specialists in the USGS-NMIC, and reported annually in the USGS-NMIC Minerals Yearbook series and in the May issue of Mining Engineering magazine. External data for these analyses were derived from industry sources, published literature, and SNL Metals & Mining, an offering of S&P Global Market Intelligence (New York, NY).
Lithium is classified as a U.S. critical mineral commodity, and its demand is projected to drastically increase through 2040, driven by electric vehicle production and energy storage applications (IEA 2021).Most global lithium production is not in the United States increasing vulnerability to a supply disruption. The U.S. Geological Survey is actively assessing domestic lithium deposits including lithium-bearing pegmatites in the Appalachian orogen. Permissive tracts for lithium pegmatite deposits were delineated by integrating lithological, tectonic, geochemical, geophysical, and mineral occurrence data. The geospatial data and permissive tracts were used to estimate the number of undiscovered lithium pegmatite deposits. Estimates were then integrated into probabilistic simulations along with a new global lithium pegmatite grade and tonnage dataset to quantify potential contained undiscovered lithium resources. An economic filter was used to estimate the amount of potentially recoverable undiscovered resources. Preliminary computations for the northern Appalachians, including application of the economic filter to the median recoverable contained resource, yields 900,000 metric tons of Li 2 O that correspond to enough Li 2 O to replace 127 years of import reliance at the current rate (7,100 t Li 2 O/yr; USGS, 2025). For the southern Appalachians, preliminary computations yielded 1,430,000 metric tons of Li 2 O, which corresponds to 201 years of import reliance.
Graphite is designated as a critical mineral by the U.S. Government due to its essential role in modern technology and its vulnerability to supply chain disruption. To evaluate domestic graphite resources, the U.S. Geological Survey (USGS) conducted two airborne electromagnetic (AEM) surveys as part of the Earth Mapping Resources Initiative (Earth MRI) over prospective areas in the southern Appalachians of Alabama and the Seward Peninsula of Alaska. These surveys aimed to refine areas of interest by revealing subsurface electrical resistivity patterns indicative of graphite-bearing rocks. The results of the AEM surveys were integrated with existing geological knowledge and supplemented by field observations to assess the likelihood of undiscovered resources in these regions. This multidisciplinary approach combined geophysical techniques with traditional geological methods, enhancing the understanding of graphite potential in areas that may have been previously overlooked. The findings from this initiative are expected to contribute significantly to the ongoing efforts to secure a reliable domestic supply of graphite, thereby reducing import reliance and supporting national interests in mineral resource management.
Society is fundamentally dependent upon commodities that are used in end-use products for the aerospace, defense, energy, telecommunication, and transportation sectors, resulting in centuries of mining to supply these commodities and materials. Waste from these mining operations can remain on the landscape indefinitely, but there is a lack of national understanding of the distribution and scale of such waste features. The renewable energy transition will continue to increase demand for critical minerals and will result in increasing volumes of mine waste on the Earth’s surface. Reprocessing mine waste can reduce environmental risks and recover needed commodities to match growing demand for societal growth. Therefore, understanding the approximate abundance of commodities that may be available for recovery within mine waste features can be an important piece of domestic critical mineral supply.